What are the differences in dosage between ritalin (methylphenidate) and adderall, to achieve the same effects?

Rough estimate below: D-amphetamine (dexedrine) is about twice as potent as methylphenidate (ritalin), so 10 mg of the former is roughly the same as 20 mg of the latter. Adderall (dextroamphetamine and racemic amphetamine) is a mixture of 1/2 d-amphetamine plus 1/2 d- & l-amphetamine (the latter being inactive with respect to adhd. So, conversion from Ritalin to Adderall (dextroamphetamine and racemic amphetamine) is about 20 mg down to 15 mg. But, individual response varies, so that's just a start.